Department of Astronomy licentiate thesis PTF12os and iPTF13bvn Two stripped-envelope supernovae discovered by the Palomar Transient Factory Author: Christoffer Fremling Supervisor: Co-supervisor: Mentor: Jesper Sollerman Claes Fransson Erik Zackrisson 20-10-2016 OKC STOCKHOLM UNIVERSITY Department of Astronomy Abstract PTF12os and iPTF13bvn Two stripped-envelope supernovae discovered by the Palomar Transient Factory by Christoffer Fremling This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF], and it is particularly closely tied to the still ongoing research on the stripped-envelope (SE) supernova (SN), iPTF13bvn (Type Ib), that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet star, but we have shown that this is very likely not the case. We suggest instead that the most likely scenario is that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion star (Paper I), in a similar way as for the very well studied Type IIb SN 2011dh. We have also investigated another SE SN, PTF12os (Type IIb), that occurred in the same galaxy as iPTF13bvn, with the conclusion that PTF12os and iPTF13bvn are very similar amongst themselves, and that both of them are also remarkably similar to SN 2011dh, in terms of all of the available observations (light-curves, spectra; Paper II). In Paper II a grid of hydrodynamical models were used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0:063 − 0:075 M⊙, ejecta masses in the range 1:85 − 1:91 M⊙, and kinetic energies in the range 0:54 − 0:94 × 1051 erg. Using the 56Ni -masses derived from our hydrodynamical modeling in combination with nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ∼ 12 M⊙ for iPTF13bvn and . 15 M⊙ for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their hydrogen envelopes and become SE SNe without binary interactions. As a by-product of this research, a fully automatic reference image subtraction photometry pipeline was also developed for the Palomar 60-inch telescope (P60; Paper II). The imaging data collected by the P60 is reduced on-the-fly by this pipeline and the resulting photometry is automatically uploaded to the web-based iPTF SN follow-up database interface hosted at CalTech. iii List of Papers The papers included in this licentiate thesis will be referred toas Paper I and Paper II. Short summaries of Papers I and II are given in Chapt. 5. Paper I, Fremling et al. (2014); Fremling, C., Sollerman, J., Taddia, F., Ergon, M., Valenti, S., Arcavi, I, Ben-Ami, S., Cao, Y., Cenko, S. B., Filippenko, A. V., Gal-Yam, A., Howell, D. A. (2014). The rise and fall of iPTF13bvn, not a Wolf-Rayet star. A&A, 565, A114. Paper II, Fremling et al. (2016); Fremling, C., Sollerman, J., Taddia, F.,Ergon, M., Fraser, M., Karamehme- toglu, E., Valenti, S., Jerkstrand, A., Arcavi, I., Bufano, F., Elias Rosa, N., Filippenko, A. V., Fox, D., Gal-Yam, A., Howell, D. A., Kotak, R., Mazzali, P., Milisavljevic, D., Nugent, P. E., Nyholm, A., Pian, E., Smartt, S. (2016). PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 5806. A&A, 593, A68. While Papers I and II are the basis of this thesis, I have also, during my PhD studies, worked on and contributed to many other projects that have lead to publications by other leading authors. These will be listed below, and I am a co-author on all of the listed papers. However, in the list below I give the first three authors only. Many of the papers below also contain analysis based on photometry produced by my automatic pipeline for host-subtraction (FPipe), presented in Paper II and Chapt. 4. These are marked with [FPipe] at the end of the entries. Papers not included in this thesis: Taddia et al. (2016a); Taddia, F., Fremling, C., Sollerman, J., et al. (2016). iPTF15dtg: a double-peaked Type Ic supernova from a massive progenitor. A&A 592, A89. [FPipe]. Taddia et al. (2015a); Taddia, F., Sollerman, J, Fremling, C., et al. (2015). Metallicity at the explosion sites of interacting transients. A&A 580, A131. Kromer et al. (2016); Kromer, M., Fremling, C., Pakmor, R., et al. (2015). The peculiar Type Ia super- nova iPTF14atg: Chandrasekhar-mass explosion or violent merger?. MNRAS 459, 4428-4439. Taddia et al. (2016b); Taddia, F.,Sollerman, J, Fremling, C., et al. (2016). Long-rising Type II supernovae from Palomar Transient Factory and Caltech Core-Collapse Project. A&A 588, A5. [FPipe]. v Goobar et al. (2014); Goobar, A., Johansson, J., Amanullah, R., et al. (2014). The Rise of SN 2014J in the Nearby Galaxy M82.. ApJ 784, L12. [FPipe]. Kankare et al. (2015); Kankare, E., Kotak, R., Pastorello, A., et al. (2015). On the triple peaks of SNHunt248 in NGC 5806. A&A 581, L4. Strotjohann et al. (2015); Strotjohann, N. L., Ofek, E. O., Gal-Yam, A., et al. (2015). Search for Precursor Eruptions among Type IIb Supernovae.. ApJ 811, 117. [FPipe]. Yuan et al. (2016); Yuan, F., Jerkstrand, A., Valenti, S., et al. (2016). 450 d of Type II SN 2013ej in optical and near-infrared. MNRAS 461, 2003-2018. Roy et al. (2016); Roy, R., Sollerman, J., Silverman, J. M., et al. (2016). SN 2012aa - a transient between Type Ibc core-collapse and superluminous supernovae. arXiv: 1607.00924.[FPipe]. Cao et al. (2016a); Cao, Y., Johansson, J., Nugent, P. E., et al. (2016). Absence of Fast-moving Iron in an Intermediate Type Ia Supernova between Normal and Super-Chandrasekhar. ApJ 823, 147. [FPipe]. Leloudas et al. (2016); Leloudas, G., Fraser, M., Stone, N. C., et al. (2016). The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole. arXiv: 1609.02927.[FPipe]. Blagorodnova et al. (2016); Blagorodnova, N., Kotak, R., Polshaw, J., et al. (2016). Common Envelope ejection for a Luminous Red Nova in M101. arXiv: 1607.08248.[FPipe]. Prentice et al. (2016); Prentice, S. J., Mazzali, P.A., Pian, E., et al. (2016). The bolometric light curves and physical parameters of stripped-envelope supernovae. MNRAS 458, 2973-3002. [FPipe]. Hosseinzadeh et al. (2016); Hosseinzadeh, G., Arcavi, I., Valenti, S., et al. (2016). Type Ibn Super- novae Show Photometric Homogeneity and Evidence for Two Spectral Subclasses. arXiv: 1608.01998. [FPipe]. vi Statement Contribution to Paper I. The author of this thesis (CF) used photometric and spectroscopic data collected by the iPTF collaboration, along with archival HST images, to perform the analysis presented in the paper. Spectra were reduced by collaborators within the iPTF. The host-subtracted photometry presented in the paper was reduced using the pipeline developed by CF (FPipe; see Chapt. 4). CF designed all figures, and wrote the entirety of the text in the paper. The hydrodynamical model fitting results presented in the paper were computed by M. Ergon. Changes were incorporated after discussing the first draft with the coauthors. Contribution to Paper II. The author of this thesis (CF) analyzed and presented results based on pho- tometric and spectroscopic data collected by the iPTF collaboration. HST archival images were analyzed by CF and M. Fraser. CF performed the astrometric progenitor identification presented in the paper, and M. Fraser performed the HST photometry and image subtractions. F. Taddia performed the metallicity measurements based on long-slit spectroscopy presented in the paper. Some of the metallicity measure- ments were based on spectra obtained via a service-mode proposal at the Nordic Optical Telescope by CF (Proposal ID 48-408, PI C. Fremling). All previously unpublished spectra of PTF12os and iPTF13bvn were reduced by collaborators within the (i)PTF collaborations. The host-subtracted photometry pre- sented in the paper was reduced using the pipeline developed by CF (FPipe; which is also presented and described in the paper). CF produced all figures from the relevant data, except Fig. 4 (provided by M. Fraser) and Fig. 1 (which is composed by CF from the original color image created by ESA/NASA/Andre van der Hoeven). CF wrote the entirety of the text in the paper, except for Sect. 5.1, which contains significant contributions from M. Fraser, and Sect. 3 which contains contributions from F. Taddia. The hydrodynamical model fitting results presented in the paper were computed by M. Ergon. Changes and additions were incorporated after discussing the first draft with the coauthors. Figures in this thesis. The figures in this thesis were created (using Gimp, Pages, MATLAB and DS9) by CF (Figures 1.3, 1.4, 1.6, 1.7, 4.1), either from scratch or based on PTF and iPTF data. Figures 2.10, 2.15, 2.18, 2.19, 2.20, 2.22, 2.26, 2.29, 2.30, 2.33, 2.35, 2.36, 2.37 have been created in the same way by CF, but these are adaptations of figures previously published in Papers I and II. Fig. 2.12 was created byM. Fraser for Paper II. Fig. 1.1 is from the internal iPTF Follow-Up Marshal webpage of iPTF13bvn. Fig. 1.2 was created by CF, based on the original color image by ESA/NASA/Andre van der Hoeven. Fig. 1.9 was created by A. Nyholm specifically for this thesis. Figures 1.5, 1.8, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.11, 2.13, 2.14, 2.16, 2.17, 2.21, 2.23, 2.24, 2.25, 2.27, 2.28, 2.31, 2.32, 2.34 are reproduced from other sources (ESO, or other published papers), sometimes with minor additions, as described in their captions.